The most common surgical orthognathic procedure is mandibular advancement to treat class II malrelationships. For almost two decades inter- maxillary fixation has been the standard post-operative stabilization technique until recently when rigid internal fixation was shown as an effective alternative. Studies on condyle position changes following orthognathic surgery have reported differing results. Post-operative condylar displacement due to difficulty in stabilizing the distal segment has been described. Although an increased risk of post-operative symptoms of temporomandibular dysfunction (TMD) associated with use of rigid fixation has been reported by many authors, there is disagreement in the literature regarding this issue. This study is designed to determine condylar position changes following mandibular advancement surgery with rigid fixation (screws). Radiographic changes in condylar position will be determined in all planes (X, Y, and Z). Computed Tomography (CT) with image reconstruction will be used, which is considered the optimum method for consistent measurement of the TMJ structures in the axial and sagittal planes simultaneously. A population of patients at The university of Texas health Science Center at San Antonio are currently undergoing mandibular advancement surgery. Twenty- four mandibular advancement patients who elect to have rigid fixation as the surgical stabilization method will be studied. CT data will be acquired in the plane with a G.E. 9800 scanner using abutting 1.5mm thick slices every 1.5mm. Radiographic data acquisition will occur one week preoperatively and eight weeks postoperatively. Measurements will be made from the image reconstructions using a Maxiview 3200 workstation. Preoperative and postoperative assessments will be made of the following condyl-fossa relationships. 1) Medio-lateral condylar position, 2) Condylar Angulation, 3) Anterior-posterior condylar position, 4) Rotational changes in condylar position. The long range goal is to provide useful information regarding the effects of mandibular advancement surgery on condylar position and related TMJ symptomatology.